Skip to main content

Full text of "The manufacture and properties of iron and steel"

See other formats

. THE. BLAST FURNACE.'-;.  .:                           65
coke .(C02-J-C=2.".GO), and a considerable amount created by tlie reduction of the iron oxides by carbonic oxide (CO). Inasmuch as any attempt to equate these conditions would involve many -assumptions, it may be as well to presuppose a uniform rate of progression.
 The reactions in the neighborhood of the tuyeres differ from the reactions occurring higher up, on account of the facilitation of chemical action by the intense temperature. The blast is composed of nitrogen and oxygen; the nitrogen passes unchanged through the zone- of fusion and the upper zones of .reduction, and escapes in its original state and quantity with the tunnel head gases. A small and uncertain quantity combines with carbon to form cyanogen, which combines with potassium or sodium to form cyanides, but these are constantly undergoing- decomposition in their passage upward through the ore, according to the reaction:
2 KCN+3 FeO=K20+2 CO+3 Fe+2 N.
The oxygen, immediately upon entering, unites with glowing coke to form carbonic acid (C02), but by contact with other pieces of incandesc'ent coke this is changed into carbonic oxide (CO),. and from a distance of about four feet above the tuyeres to the point where limestone is decomposed "and ferrous oxide reduced, there is no carbonic acid in the furnace, the entire atmosphere being composed of nitrogen and carbonic oxide (CO). The coke comes down through the furnace unchanged and unaffected in quality or quantity, save for the oxidation of a small amount by the carbonic acid (C0*>) from, the limestone, until it reaches a point about four feet above the tuyeres, when it meets the carbonic acid (C02) formed at the tuyeres, and there then occurs the reaction :
=2 CO.
At the same time other particles of ' incandescent carbon, possibly only a fraction of an inch away from where the foregoing reaction is taking place, are coming in contact with molecules of free oxygen from 'the blast, and' there occurs the following reaction;
' C+2 0=00,,'          _        _  ....... ''_